readme improvements
switched to smtp mail sending and improvements to dockerfile
only refactoring: BundleChecker (some comments, better variable names), more consistent names for symbols.
refactoring BundleChecker: split to modules, nicer error handling
Merge https://github.com/factisresearch/Frozone

Conflicts:
	src/Frozone/BundleChecker.hs
	src/Frozone/Types.hs